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Wet‐design AC subsea power cables are currently rated up to a maximum voltage of 72.5 kV. These high voltage (HV) cables are cost‐effective alternatives to subsea cables kept dry by a protective lead sheath and exhibit superior properties for dynamic applications. However, several vented water trees, degradation phenomena reducing the cable lifetime, are observed in a HV XLPE insulated cable subjected to wet aging in the laboratory. The water trees initiate from a smooth and clean XLPE insulation/semiconductive screen interface. In this paper, we show that voids in the range 15–150 μm are observed in the conductor screen, 50–320 μm from the water tree inception sites. Degradation of the semiconductive material is observed, in the form of porous regions that connect the voids to the water tree inception sites. NaCl impurities are detected on the void surfaces and in the porous regions. These features are proposed to be the pre‐requisites for the formation of the vented water trees observed in this type of cable. The mechanism responsible for the formation of the void and porous regions in the semiconductive cable screen is discussed based on the observations. [ABSTRACT FROM AUTHOR]

The development of marine resources is intrinsically linked to the utilization of various marine equipment. Among these, marine pipelines and cables are crucial for the exploitation of deep-sea oil and gas resources. Mooring cables, marine towed cables, marine umbilical cables, submarine cables, and marine pipelines are typical slender and flexible marine components. These slender marine flexible members present various dynamic challenges during laying, installation, and in-position operation. Facing these challenges, scholars from China and around the globe have explored theoretical, numerical, and experimental solutions to these challenges. The conclusions need to be condensed to improve their practical and academic value for engineering applications. This paper summarizes the explorations and provides general design methods and concepts of marine pipelines. Additionally, this paper looks forward to the future development trend of marine pipelines in engineering applications as well as theoretical research. The aim is to provide a reference for the research of underwater pipelines and cables. [ABSTRACT FROM AUTHOR]

In this study, we propose a CNN-GAN-based real-time processing technique for filtering images of underwater cables used in power systems. This addresses the excessive interference impurities that are frequently observed in images captured by remotely operated vehicles (ROVs). The process begins with the input of the original image into the convolutional neural network (CNN). Subsequently, the training outcomes, which serve as input parameters for the generative adversarial network (GAN), facilitate the filtering process. The system also calculates both the structural similarity index measure (SSIM) and peak signal-to-noise ratio (PSNR), performing model updates via backward propagation. This technique utilizes deep learning technologies to achieve rapid, real-time filtering of underwater cable images. The experimental results reveal that the loss function of the CNN reaches 0.16 with an accuracy of 97.5%, while the loss function of the adversarial GAN network approaches 0.05. Compared with traditional methods such as DDN, JORDOR, RESCAN, and PRENet, the proposed CNN-GAN algorithm exhibits superior performance, as evidenced by the higher PSNR and SSIM values. Specifically, for clear water images, the PSNR reaches 29.86 dB and the SSIM is 0.9045. For severely polluted images, the PSNR is 28.67 dB and the SSIM is 0.8965, while for unevenly illuminated images, the PSNR and SSIM values are 24.37 dB and 0.88, respectively. These enhancements significantly benefit the monitoring and maintenance of power systems. [ABSTRACT FROM AUTHOR]

Towing cable arrays have made significant contributions across various fields, and their outspread process is crucial for realizing their functionalities. However, research on the dynamic characterization of the outspread process of towed cable arrays lacks systematic organization. This paper reviews, organizes, and analyzes the outspread process of towing cable arrays, drawing on relevant models, case studies, and structural features. It ingeniously applies concepts from parachute outspread to the analysis of towing-cable-array deployment. The study systematically examines the deployment of towing cable arrays under varying cable lengths, wave conditions, and the interactions between line arrays. The goal is to integrate existing research on the outspread of towing cable arrays, addressing the gaps in the description of this process and providing a comprehensive analysis of the outspread characteristics under different conditions. Additionally, this paper identifies current limitations in this area and provides insights for future developments. Furthermore, it explores the potential application of AI to address these challenges. The aim of this paper is to contribute meaningfully to this field. [ABSTRACT FROM AUTHOR]

This study investigates the tracking of underwater cables using autonomous underwater vehicles (AUVs) equipped with side-scan sonar (SSS). AUV motion stability is crucial for effective SSS imaging, which is essential for continuous cable tracking. Traditional methods that derive AUV guidance rates directly from measured cable states often cause unnecessary jitter when imaging, complicating accurate detection. To address this, we propose a non-myopic receding-horizon optimization (RHO) strategy designed to maximize cable imaging quality while considering AUV maneuvering constraints. This strategy identifies the optimal heading decision sequence over a future horizon, ensuring stable and efficient cable tracking. We also employ a long short-term memory (LSTM) network to predict future cable states, further minimizing AUV motion instability during abrupt path changes. Given the computational limitations of AUVs, we have developed an efficient decision-making framework that can execute resource-intensive algorithms in real time. Finally, the robustness and effectiveness of the proposed algorithm were validated through comparative experiments. The results demonstrate that the proposed method outperforms existing methods in key metrics such as cable-tracking accuracy and AUV motion stability. This ensures that the AUV can acquire high-quality acoustic images of the submarine cable in an optimal state, enhancing the continuity and reliability of cable-tracking tasks. [ABSTRACT FROM AUTHOR]

To mitigate accidents in submarine cable construction within the rapidly expanding offshore wind power sector, this study employed the analytic hierarchy process (AHP) and risk matrix method (LS) to assess the risks associated with identified factors. Based on project research and expert consultations, five primary and twenty-two secondary risk factors were identified. AHP was utilized to rank the primary risk factors by severity, probability, and detection difficulty, with the highest risk being the environmental impact, followed by third-party destruction and worker error. LS was applied to rank the secondary risk factors by likelihood and severity, with the highest risks being complex submarine topography, low underwater visibility, and fishing operations. The study proposes risk reduction measures based on these evaluations and offers methodological guidance for improving construction safety in similar enterprises. [ABSTRACT FROM AUTHOR]

Over recent years, the emergence of the offshore wind sector has spurred much interest in subsea cables. The predominant failure modes of subsea cables are associated with extreme environmental conditions. Wave-forcing during severe storms is less expected and causes more damage. A generalized multiphysics cable model is constructed to predict the movement, damage, and lifetime of subsea cables subject to dynamic wave and current action due to abrasion and corrosion. The present cable lifespan prediction model extended the previous tide-only model by considering the contribution of hydrodynamic forces by waves and the effect of wave and current incident angle relative to the cable. The predicted cable sliding distance at each section of the cable is combined with the Archard abrasion wear model and the corrosion model to predict the loss of cable protective layers and the resulting expected lifespan of the cable. The model is the first of its kind that can predict the spatial variation of wave and current loading, cable movement, damage, remaining lifetime, and cable failure modes and location. In addition, spatial and temporal variations of magnitude and direction of wave, current, and tide can be incorporated into the model for realistic large-scale simulations of cable performance in field conditions. The model compares well with previous laboratory experiments and numerical models. The present model was applied for the first time to the European Marine Energy Centre (EMEC)'s wave test site located at Billia Croo off the west coast of mainland Orkney, Scotland, and validated by the cable lifespan data. The 1-year and 100-year return period wave height and period and the average wave and tide conditions are used to drive the present cable lifespan model. It was found that the cable movement is predominantly driven by waves, and the previous tide-only model would predict zero cable movement, indicating the importance of the incorporation of wave contribution into the cable model. Furthermore, besides wave height and period, the wave angle relative to cable was found to be a determining factor for the cable movement and lifespan. The present multiphysics cable model provides a new capability to predict 70% of failure modes currently not monitored in situ and to deploy, plan, and manage subsea cables with improved fidelity, reduced cost, and human risk. [ABSTRACT FROM AUTHOR]

The frequency‐domain reflection (FDR) has been demonstrated to be a trustworthy technique in solving the defect location of power cable by field experiments. However, the location spectrum of the FDR requires manual window smoothing and can be disturbed by spurious peaks. Aiming at these shortcomings of FDR, a new method of cable defect location based on Burg power spectral (BPS) is introduced in this paper. The idea of this method is to use linear difference variance to fit the distribution of reflection coefficient spectrum and build an auto‐regressive (AR) model. The Burg algorithm is employed to estimate the coefficients model and calculate the power distribution of the AR model. Then, the cable defects will be located by BPS with high precision and resolution. In this method, the fast Fourier transform (FFT) with windowed function is replaced by an AR model without windowed function. This suppressed the impact of spurious peaks or spectrum leakage in FFT on the localization defects, and the localization resolution is higher. Finally, we validate the feasibility and effectiveness of BPS through experiments conducted on a 500 m laboratory cable and a 9.6 km submarine cable. [ABSTRACT FROM AUTHOR]

This survey provides a comprehensive review of underwater cable detection and tracking literature, identifying key problem types and highlighting unique underwater challenges. It emphasizes the critical role of underwater cable detection in global communications and energy infrastructures, addressing complexities like low visibility and variable sea conditions. The analysis compares the efficacy of various models, particularly deep learning approaches like CNNs and Transformers, in adapting to underwater imagery challenges. A new roadmap for efficient cable detection and tracking systems is proposed, focusing on multimodal data integration and nonoptical detection methods. Importantly, the study includes performance evaluations of state‐of‐the‐art models on custom underwater datasets, offering practical insights. The survey's findings are validated through an implementation of an underwater object‐tracking model incorporating effective algorithms from the literature. [ABSTRACT FROM AUTHOR]

The partial exposure of submarine cable may cause damage to the metal sheath, which will affect its safe and stable operation. Existing detection methods for burial depth of submarine cables are difficult to implement and have a long detection period. In this contribution, a method is proposed to calculate the burial depth of alternating current (AC) submarine cable based on surface optical fiber monitoring temperature. According to the functional relationship between the transient temperature rise of submarine cable outer sheath above the ambient temperature and the burial depth (in the IEC‐60853 standard), the burial depth of submarine cables is calculated. The optical fiber temperature, electric load and meteorological temperature data are used for 30 consecutive days in September 2020 to calculate the change of burial depth of AC 500 kV oil‐filled submarine cable. The calculation results are basically consistent with the detection conclusion of side‐scan sonar, which shows that the method can accurately calculate the burial depth of submarine cables and locate the exposed position. This provides a theoretical basis for the intelligent operation and maintenance of AC submarine cables. [ABSTRACT FROM AUTHOR]

This study addresses the limitations of traditional methods used to analyze factors influencing submarine cable burial depth and emphasizes the underutilization of cable construction data. To overcome these limitations, a machine learning-based model is proposed. The model utilizes cable construction data from the East China Sea to predict the weight of factors influencing cable burial depth. Pearson correlation analysis and principal component analysis are initially employed to eliminate feature correlations. The random forest method is then used to determine the weights of factors, followed by the construction of an optimized backpropagation (BP) neural network using the ISOA-BP hybrid optimization algorithm. The model's performance is compared with other machine learning algorithms, including support vector regression, decision tree, gradient decision tree, and the BP network before optimization. The results show that the random forest method effectively quantifies the impact of each factor, with water depth, cable length, deviation, geographic coordinates, and cable laying tension as the significant factors. The constructed ISOA-BP model achieves higher prediction accuracy than traditional algorithms, demonstrating its potential for quality control in cable laying construction and data-driven prediction of cable burial depth. This research provides valuable theoretical and practical implications in the field. [ABSTRACT FROM AUTHOR]

Hydrogen production is a vital development trend to improve the economics and penetration rate of offshore wind farms (OWFs), and distributed hydrogen production (DHP) is a preferred solution for deep and far sea OWFs without expensive submarine cables and offshore substations. The export pathway of OWF-DHP consists of collection pipelines, transmission pipelines, and offshore compressor stations. In this paper, mathematical programming is introduced to explore the export pathway planning problem of OWF-DHP. Firstly, the area of OWF is discretized into multiple grids with the center of the grids being the candidate locations of the offshore compressor station. Then, a binary integer quadratic programming problem is established to optimize both the offshore compressor station location and pipeline construction with different topologies. Further, the mathematical model is solved by the branch and cut algorithm integrated with the proposed dimension reduction methods. Finally, the effectiveness of the proposed export pathway planning approach is verified by the actual data of Baltic Eagle OWF in Germany, which would support the construction of the OWF-DHP project. [Display omitted] • Studying export pathway planning (EPP) for OWF-distributed hydrogen production. • Introducing mathematical programming to model EPP as a BIQP problem. • Proposing dimension reduction methods to accelerate BIQP problem solving. • Verifying the effectiveness of the EPP approach with the Baltic Eagle OWF case. • Conducting sensitivity analysis on transportation carrier and pipeline topology. [ABSTRACT FROM AUTHOR]

During the construction of offshore wind farms (OWFs), the capital cost associated with the collector system topology (CST) constitutes a significant proportion of the overall investment. A more efficient solution for connecting submarine cables can lead to substantial cost savings. To address this challenge, this paper introduces a novel approach that divides wind turbines into groups by polar coordinates to satisfy the no cross constraint. Subsequently, meta-heuristic algorithms are employed to optimize the grouping arrangement through iterative processes. In this way, the complex high-dimensional and multi-parameter problem will be decomposed into multiple parts for resolution. This paper evaluates four optimization algorithms to compare their effectiveness in optimizing the grouping results. Two different OWF scenarios are considered in the case studies to assess the performance of the proposed algorithms. Through extensive simulations and case studies, the results demonstrate the effectiveness and robustness of proposed approaches in achieving high-quality solutions while satisfying the constraints imposed by OWF operations and environmental conditions. Among the four algorithms, the immune algorithm stands out for its superior ability to provide more cost-effective solutions, which suggest that the immune algorithm-based optimization method can significantly contribute to the design and development of efficient CST for OWFs. [ABSTRACT FROM AUTHOR]

In the nearshore area, ocean current display intricate complexities due to interactions among tide, river, and coastline, which makes accurate current modeling challenging. Continuous in situ observation with high spatial and temporal resolution helps to better understand the dynamics of these currents. In this study, we used a 10‐km long submarine fiber‐optic cable with distributed acoustic sensing technology to record seismic signals associated with ocean waves. The current velocity and water depth were obtained from the velocity dispersion using frequency‐wave number analysis matched against theoretical ocean wave propagation equations. The results show remarkable agreement with observation of a nearby current meter, confirming the dominance of tidal currents as well as a small‐scale residual current. The temporal variation of water depth is consistent with observation by a nearby tidal gauge. This study demonstrates the potential of using submarine fiber‐optic cable for long‐term, high‐resolution, near real‐time nearshore current monitoring. Plain Language Summary: The ocean currents in the nearshore area are complicated due to coastlines, seabed topography, and other factors. The complexity makes it crucial to monitor high‐resolution currents. However, it is challenging to observe them in situ with high temporal and spatial resolution over long periods using conventional methods. The novel distributed acoustic sensing technology can turn submarine fiber‐optic cables into high‐density vibration sensors. This allows us to sense nearshore ocean wave pressure loading and obtain the propagation speed of ocean waves. Ocean waves propagate faster in the direction of the current than in the opposite direction. Therefore, the current velocity can be obtained by measuring the difference of propagation speed of ocean waves in different directions along the fiber‐optic cable. In this study, we used a 10‐km long submarine fiber‐optic cable in the Yellow River Delta to conduct submarine seismic observations. We obtained the current velocity with a temporal resolution of 5 min during a 25‐day period. The reliability and strengths of our method were verified by comparison with other observations. This study demonstrates that integrating our approach with submarine fiber‐optic cables can offer an innovative approach for high‐resolution ocean current monitoring in the nearshore area. Key Points: We obtained the velocity of landward and oceanward ocean waves from in situ data recorded by distributed acoustic sensing on a submarine fiber‐optic cableWe propose a near real‐time method to monitor current and water depth for the asymmetry of ocean wave propagationThe obtained tidal current agrees with a nearby observation and the residual current pattern reveals a small‐scale eddy [ABSTRACT FROM AUTHOR]

The international network of submarine cables plays a crucial role in facilitating global telecommunications connectivity, carrying over 99% of all internet traffic. However, submarine cables challenge digital sovereignty due to their ownership structure, cross-jurisdictional nature, and vulnerabilities to malicious actors. In this article, we assess these challenges, current policy initiatives designed to mitigate them, and the limitations of these initiatives. The nature of submarine cables curtails a state’s ability to regulate the infrastructure on which it relies, reduces its data security, and threatens its ability to provide telecommunication services. States currently address these challenges through regulatory controls over submarine cables and associated companies, investing in the development of additional cable infrastructure, and implementing physical protection measures for the cables themselves. Despite these efforts, the effectiveness of current mechanisms is hindered by significant obstacles arising from technical limitations and a lack of international coordination on regulation. We conclude by noting how these obstacles lead to gaps in states’ policies and point towards how they could be improved to create a proactive approach to submarine cable governance that defends states’ digital sovereignty. [ABSTRACT FROM AUTHOR]

The retracting and releasing cables were the only link between the submarine exploration equipment and the ship, had the functions of power, information transmission and load-bearing, and were widely used in all kinds of launch and recovery systems. The safety and reliability of retracting-releasing cables were of the core functional requirements. Therefore, conducting experiments on mechanics properties of retracting-releasing cables was the foundation of retracting-releasing cable research. Starting from the types and failure modes of ocean winches and retracting-releasing cables, the state of experimental studies of the mechanics properties of retracting-releasing cables was systematically summarized, and an outlook on future research directions was provided. Firstly, the functions of ocean winches and retracting-releasing cables were categorized, followed by a detailed analysis of the forms and reasons for their failures. Secondly, the operating conditions, mechanics performance requirements of retracting-releasing cables, and experimental researchs current status were described. Lastly, the research directions for the mechanics properties of retracting-releasing cables in ocean detection equipment were discussed, including the impact and mechanism of extreme operating environments on mechanics properties of synthetic retracting-releasing cables, the behavior and mechanism of synthetic retracting-releasing cable damage under multiple load couplings, and the technology and integrated simulation devices for retracting-releasing cable mechanics properties. [ABSTRACT FROM AUTHOR]

Time-shifted seismic research plays an important role in monitoring changes in the gas-water interface uplift, the weakening of amplitude attributes, and gas distribution due to mining. When time-shifted seismic research involves non-repeatable data with significant differences between data sets due to variations in seismic data acquisition parameters and seismic geometries, it necessitates consistent processing before time-shifted monitoring comparisons. In this paper, a study of time-shifted seismic monitoring using two non-repetitive data sets based on the ocean bottom cable (OBC) and towed streamer data is presented. First, amplitude, frequency, wavelet, and time difference are processed to achieve consistency for time-shifted comparisons. Secondly, three modes of seismic geometry normalization are compared to optimize the appropriate offset, azimuth, and signal-to-noise ratio (SNR). Finally, after eliminating the fault surface wave, the maximum trough amplitude attribute is extracted for the same position in the two data sets to analyze time-shifted differences under the three modes using the ratio method and difference method. The conclusions show the following: the OBC and towed streamer data can achieve consistency in terms of amplitude, frequency, wavelet, azimuth, SNR, and time difference; the data reconstruction method outperforms other methods in normalizing offset, azimuth, and SNR; and the time-shifted comparison method of the amplitude attribute ratio method proves more effective than the difference method. This study offers a reliable foundation for future time-shifted seismic research with non-repetitive data to monitor changes in subsurface oil and gas. It also provides a methodological basis for carbon capture and storage (CCS) monitoring technology. [ABSTRACT FROM AUTHOR]

Abstract The partial exposure of submarine cable may cause damage to the metal sheath, which will affect its safe and stable operation. Existing detection methods for burial depth of submarine cables are difficult to implement and have a long detection period. In this contribution, a method is proposed to calculate the burial depth of alternating current (AC) submarine cable based on surface optical fiber monitoring temperature. According to the functional relationship between the transient temperature rise of submarine cable outer sheath above the ambient temperature and the burial depth (in the IEC‐60853 standard), the burial depth of submarine cables is calculated. The optical fiber temperature, electric load and meteorological temperature data are used for 30 consecutive days in September 2020 to calculate the change of burial depth of AC 500 kV oil‐filled submarine cable. The calculation results are basically consistent with the detection conclusion of side‐scan sonar, which shows that the method can accurately calculate the burial depth of submarine cables and locate the exposed position. This provides a theoretical basis for the intelligent operation and maintenance of AC submarine cables.

Abstract The full understanding of the importance of submarine cables as part of the global network infrastructure in the digital economy era, along with decades of knowledge accumulation in this field, has not prevented Hong Kong from facing increasing difficulties in gaining more access to submarine cable systems since 2017. Given that geopolitical differences between China and the U.S. are dividing the international network infrastructure, the business interests of Hong Kong enterprises and the urban development prospects of the Hong Kong government have been forced to defer to Beijing’s security concerns. Meanwhile, in recent years China has been acquiring data power by modelling the “data collection – data sharing – data space governance” path that the United States and its allies set previously. During this process, the power shaped by China’s unique technological, social and institutional characteristics offers an alternative to American dominance, although it exacerbates the global divergence of internet infrastructure. Many projects along the Belt and Road Initiative and the Digital Silk Road are the examples of China’s data power projection, and will bring opportunities for Hong Kong’s own submarine cables sector and for the city’s role as a super connector in the coming years.

To meet the need of electric power and communication connection between waterborne integrated vessel and underwater immersed tube during the installation process of immersed tube tunnel of the Shenzhen -Zhongshan Link, an underwater umbilical cable penetrating and connecting technology was proposed. Through the simulation and testing of key indexes such as underwater sealing performance and load-bearing performance, the results indicate that the system can meet the pressure sealing requirements for water depth of 300 meters and has a tensile resistance of 14 kN. This technology provides effective technical support for the installation of immersed tubes in the Shenzhen-Zhongshan Link, and its reliability has been verified in the installation of the Shenzhen -Zhongshan Link immersed tube tunnel. Meanwhile, it can provide technical reference for the communication connection "between vessel and immersed tube" during installation of immersed tube tunnel in larger water depth in the future. [ABSTRACT FROM AUTHOR]

Expanding floating wind into new markets could support emission reduction targets in several national contexts. It furthers the need for adequate assessments to gain a full understanding of the technology's potential in future markets. South Africa is a prime case study as it has seen limited industry and policy developments despite its huge technical potential for floating offshore wind (FOW). This paper assessed the locational potential of floating wind in South Africa through a three-phased approach that evaluated the key technical drivers/barriers of the technology, conducted a Geographic Information System analysis (GIS) using ArcMap 10.8 to exclude unsuitable sites based on a predetermined exclusion criteria (including marine protected zones, underwater cables, major oil and gas deposits, etc.), and estimated the total harvestable capacity in the feasible sites. The study found that 2% (246,105.4 km2) of South Africa's entire Exclusive Economic Zone (EEZ) is suitable for hosting floating wind turbines, with a potential to generate a maximum of 142.61 GW of floating wind power. Although the Western Cape province holds the highest potential (80.52 GW) for floating wind in the country, the Eastern Cape region, with a locational potential of 20.04 GW, is considered most suitable for early-stage developments due to the availability of grid connection points, limited marine traffic, and proximity to appropriate port facilities. Future work can conduct techno-economic assessments to evaluate the technical and economic implications of developing floating wind in distinct sites in the country's EEZ. [ABSTRACT FROM AUTHOR]

Featured Application: This article shows the research that was conducted on the motion response patterns and computational modeling results of a submersible towed system when the cables are extended and retracted during movement. This information is advantageous for actual engineering applications, facilitating enhanced control systems for depth stability, shock resistance, approach avoidance, and collision avoidance. Furthermore, it provides theoretical justification and practical illustrations to streamline the equations of motion during composite maneuvering motions. Submersible underwater towed systems usually need to transition from steady-state motion to maneuvering motion during operation while dynamically adjusting the length of the towed cable. The lumped mass approach was employed to convert the dragged cable into a model with a concentrated mass. Analyzed utilizing a computational simulation tool, the motion response of the towed system was examined for both simple and composite maneuvering motions. By comparing the changes in tension at the end of the towed cable and the depth of the towed body motion under different motion states and cable retraction and deployment speeds, the motion response law of the system when the length of the towed cable changes during the submarine maneuver motion is obtained. The maximum tension value occurred at 1.0 m/s during the acceleration maneuver when the velocity change of the submersible ended at the same time as the cable length change. After the deployment maneuver in a circular rotating motion, the range of tension fluctuations decreased by 93%, greatly improving the stability of the towed system. An analysis was conducted to examine the impact of various motion and structural parameters on the motion response. The study revealed that the buoyancy-to-gravity ratio of the towed body, the acceleration time of the accelerated motion, and the rotational speed of the circular rotational motion had a notable influence on the outcomes. When the buoyancy-to-gravity ratio of the towed body is 1.0, the maximum tension value of the towed cable is minimized, and the depth change of the towed body is closer to 0 m. [ABSTRACT FROM AUTHOR]

AbstractHorizontal wells have the advantages of high production, considerable access to reserves, and effective sand production control; thus, they are potential well types for hydrate exploitation. In the process of hydrate mining, the decomposition of hydrate will cause the deterioration of the mechanical properties of the reservoir, which may induce submarine landslides, especially in the case of multiple horizontal wells, and the risk of submarine landslides is further increased. Therefore, it is necessary to study the influence of the horizontal well pattern adopted for hydrate mining on the stability of submarine slopes. First, a triaxial mechanical experiment of gas hydrate-containing sediments was carried out, and the mechanical parameters of the hydrate-containing sediments were obtained. Second, a thermal-fluid-solid multifield coupling model considering the hydrate phase transition during the production process was established. Finally, on the basis of the finite element strength reduction method, a slope stability evaluation model for hydrate extraction from a horizontal well pattern was established, and the influence of hydrate extraction from horizontal wells on the stability of submarine slope was analyzed. The results show that the peak strength, elastic modulus and cohesion of gas hydrate-containing sediments increase with increasing hydrate saturation. In the process of hydrate exploitation via horizontal wells, with the reduction in well spacing and the increase in the number of production wells, the risk of slope instability increases. Wells positioned along the slope strike are more conducive to slope stability than those positioned perpendicular to the slope strike. The slope stability increases gradually as the slope dip decreases. When the number of wells is the same, the slope stability increases gradually with increasing well spacing and production pressure. [ABSTRACT FROM AUTHOR]

In this paper, we establish the theoretical framework for understanding the sensing capabilities of megameter-long submarine optical cables. We show the distinct advantage of polarization over phase in detecting sub-hertz environmental processes. Subsequently, we propose a scheme capable of extracting the spectrum of perturbations affecting a specific section at any position along an optical fiber by detecting the state of polarization of the backreflected light. We discuss two examples of earthquake detection and the detection of sea swells and ocean tides through the analysis of the state of polarization of an optical signal reconstructed by the receiver of a transoceanic cable, obtained from an online database [Z. Zhan, "Curie Data - Zhan et al. (2021)" (2020)]. Finally, we provide the analytical expression for the cross correlation of the polarization perturbations of two wavelength division multiplexed channels and show that the analysis of the polarization correlations between adjacent channels can provide valuable insights into the localization of earthquakes. [ABSTRACT FROM AUTHOR]

The full understanding of the importance of submarine cables as part of the global network infrastructure in the digital economy era, along with decades of knowledge accumulation in this field, has not prevented Hong Kong from facing increasing difficulties in gaining more access to submarine cable systems since 2017. Given that geopolitical differences between China and the U.S. are dividing the international network infrastructure, the business interests of Hong Kong enterprises and the urban development prospects of the Hong Kong government have been forced to defer to Beijing's security concerns. Meanwhile, in recent years China has been acquiring data power by modelling the "data collection – data sharing – data space governance" path that the United States and its allies set previously. During this process, the power shaped by China's unique technological, social and institutional characteristics offers an alternative to American dominance, although it exacerbates the global divergence of internet infrastructure. Many projects along the Belt and Road Initiative and the Digital Silk Road are the examples of China's data power projection, and will bring opportunities for Hong Kong's own submarine cables sector and for the city's role as a super connector in the coming years. [ABSTRACT FROM AUTHOR]

The arrival of the nuclear age highlighted the inadequacy of U.S. and allied information networks for transmitting vital messages across the globe. Submarine cables could be cut and radio easily jammed. U.S. and allied officials looked to emerging space technologies to compensate for the inadequacies of radio and submarine cables and to reduce their dependence on terrestrial telecommunications hardware. But satellites were also vulnerable and insufficient for meeting all communications requirements. Consequently, creating layered telecommunications networks that stretched from under the sea, across the land, and into space emerged as the optimal strategy for strengthening information security. [ABSTRACT FROM AUTHOR]

The laying of power cables is a crucial aspect of developing and maintaining modern electrical infrastructure, which is vital for transmitting electricity reliably and efficiently. This review discusses the challenges and advancements in cable laying technologies, emphasizing the critical role of these techniques in meeting the increasing demands for power transmission in the backdrop of the global shift to renewable energy. Three main traditional cable laying methods are explored, including underground, overhead, and submarine, each suited to specific environmental and operational conditions. Then, the cable faults due to the impropriate laying process are discussed. Subsequently, the challenges and advancements encountered in cable laying processes are investigated, especially the difficulties of the cable laying of underground cable, submarine cable, and high-temperature superconductivity cable. This review also considers the impact of technological innovations on improving efficiency in cable laying processes, highlighting the advances driven by digitalization and automation. [ABSTRACT FROM AUTHOR]

With the development of the social economy and the improvement of electrification, cables and wires play an important role in people's lives and industrial development. Meanwhile, the large-scale laying of cables has also made them a fire hazard that cannot be ignored in land construction such as residential buildings, utility tunnels, nuclear power plants, refineries, marine systems such as submarines and ships, and airborne systems such as spacecrafts and aircrafts. In this work, studies on fire the characteristics of cables and wires over the last decades have been reviewed. Based on different experimental forms and objects (laboratory wires and commercial cables), this paper summarizes the theories of the fire dynamics in wire combustion, including the models of ignition and flame propagation, the criteria for blowing off and quenching, and the critical conditions for dripping behavior. The effects of materials, layouts, and environments on wire combustion phenomena such as airflow, ambient pressure, oxygen, gravity, and orientation angle have been discussed in detail according to the theories of heat transfer and combustion. In addition, test standards and studies on the fire behavior and release of toxic gases of commercial cables have also been fully described. Through the summary of the above content, it is expected to build a preliminary theoretical framework and future research directions for researchers in the field of cable fires. [ABSTRACT FROM AUTHOR]

The grounding circulation current of the sheath and armour of single‐core AC submarine cables is high during operation, which can easily cause insulation damage and faults. Traditional methods that only monitor the amplitude of grounding circulation current make it difficult to detect defects in the cables, so further research is needed on the mathematical mechanism and detection methods of grounding circulation current. A mathematical model for the capacitance and impedance coupling of a single‐core submarine cable was established, and the influence of factors such as active power, length of armour stripping section, armour resistivity, armour magnetic permeability and grounding resistance on the grounding circulation current was analysed. A method for identifying abnormal grounding circulation current of submarine cables based on the combination of amplitude and phase was proposed. [ABSTRACT FROM AUTHOR]

Full-waveform inversion (FWI) has emerged as the state-of-the art high resolution seismic imaging technique, both in seismology for global and regional scale imaging and in the industry for exploration purposes. While gaining in popularity, FWI, at an operational level, remains a heavy computational process involving the repeated solution of large-scale 3-D wave propagation problems. For this reason it is a common practice to focus the interpretation of the results on the final estimated model. This is forgetting FWI is an ill-posed inverse problem in a high dimensional space for which the solution is intrinsically non-unique. This is the reason why being able to qualify and quantify the uncertainty attached to a model estimated by FWI is key. To this end, we propose to extend at an operational level the concepts introduced in a previous study related to the coupling between ensemble Kalman filters (EnKFs) and FWI. These concepts had been developed for 2-D frequency-domain FWI. We extend it here to the case of 3-D time-domain FWI, relying on a source subsampling strategy to assimilate progressively the data within the Kalman filter. We apply our strategy to an ocean bottom cable field data set from the North Sea to illustrate its feasibility. We explore the convergence of the filter in terms of number of elements, and extract variance and covariance information showing which part of the model are well constrained and which are not. Analysing the variance helps to gain insight on how well the final estimated model is constrained by the whole FWI workflow. The variance maps appears as the superposition of a smooth trend related to the geometrical spreading and a high resolution trend related to reflectors. Mapping lines of the covariance (or correlation matrix) to the model space helps to gain insight on the local resolution. Through a wave propagation analysis, we are also able to relate variance peaks in the model space to variance peaks in the data space. Compared to other posterior-covariance approximation scheme, our combination between EnKF and FWI is intrinsically scalable, making it a good candidate for exploiting the recent exascale high performance computing machines. [ABSTRACT FROM AUTHOR]

To assess the insulation aging in high-voltage XLPE submarine cables using frequency domain dielectric spectroscopy, this study presents a methodology for separating the polarization and conductance components from the dielectric response data by analyzing the physical significance of the complex dielectric constant. Initially, four sets of samples of high-voltage XLPE submarine cables exhibiting varying degrees of aging were procured, which were generated through accelerated aging tests and measured the mechanical properties and frequency domain dielectric spectra of these samples. Subsequently, the polarization and conductance components were separated from the measured dielectric curves to investigate the impact of aging on polarization and conductivity losses within the low-frequency range. Finally, the precision of the dielectric model in reconstructing the measured dielectric curves was compared, and characteristic parameters for quantifying the aging condition were suggested. The discoveries indicate that the polarization and conductance processes in the dielectric response of high-voltage XLPE submarine cables accelerate with increasing aging, and removing the conductivity loss from the imaginary part of the complex dielectric constant enhances the accuracy of the dielectric model in reconstructing the measured dielectric curves. The model parameters ∆ε, ε∞, and α can effectively characterize the aging state of XLPE insulation in high-voltage submarine cables, enabling the assessment of aging insulation in high-voltage XLPE submarine cables. [ABSTRACT FROM AUTHOR]

Subsea infrastructure is typically out of sight, but in recent times, seldom out of mind. The sabotage of the Nord Stream pipelines in October 2022 has magnified the vulnerability and critical importance of subsea infrastructure. It also exposed a lack of understanding on how subsea networks operate, how they are regulated, who controls them and how they are protected. Ireland matters in this context. Despite its official policy of neutrality, Ireland occupies an important strategic position in terms of transatlantic telecommunications cables between the United States, Britain and continental Europe. The conflict in Ukraine has amplified tensions in this context in terms of the increased threat of grey-zone/hybrid warfare activity. This article will consider for the first time how a global connectivity hub on the western periphery of Europe governs critical underwater infrastructure. It will discuss the context and agencies involved in subsea cable governance in Ireland and identify the gaps in this protection before formulating suggestions for the long-term improvement of Ireland's maritime security capacity. The Irish case is important as it can help inform defence policy and security practice in other island states with large maritime jurisdictions and in particular states with small navies. [ABSTRACT FROM AUTHOR]

To process magnetic anomaly data, appropriate parameters for field separation, denoising, and Euler deconvolution must be manually selected. The traditional workflow is inefficient and cannot fulfill the rapid detection of submarine cables due to complex processing and manual parameter tuning. This study presents an end-to-end deep learning approach for the identification and positioning of submarine cables based on magnetic anomalies. The proposed approach effectively establishes a direct mapping correlation between the magnetic field data and the position of the submarine cable. Synthetic tests suggest that our method performs better in terms of positioning accuracy than the conventional Euler method. Our results for the field data are comparable to those obtained using conventional techniques. Furthermore, the proposed method achieves an optimal solution by employing a clustering technique and selecting the solution with the maximum confidence, which avoids spurious solutions associated with traditional methods. The proposed method can directly determine the position of the submarine cables using the raw magnetic field data. Contrary to the traditional processing workflow, field separation and denoising are not necessary in this novel approach, resulting in higher processing efficiency and a simpler processing process. [ABSTRACT FROM AUTHOR]

This article introduces the latest features and enhancements in TopoHub, an open repository for network topologies used in networking research. The major update includes a new collection of global-scale backbone topologies, generated based on population density and incorporating submarine communication cables. The web interface has been upgraded to support interactive exploration of networks, including panning and zooming. Additionally, the new version addresses usability improvements and bug fixes informed by user feedback, enhancing the overall functionality and user experience of the platform.

Mass-impregnated (MI) cables have been used for many years as cables in high-voltage direct current (HVDC) systems. In line commutated converter (LCC) HVDC systems, polarity reversal for power flow control can induce significant electrical stress on MI cables. Furthermore, the mass oil and kraft paper comprising the impregnated insulation have significantly different coefficients of thermal expansion. Load fluctuations in the cable lead to expansion and contraction of the mass, creating pressure within the insulation and causing redistribution of the impregnant. During this process, shrinkage cavities can form within the butt gaps. Since the dielectric strength of the cavities is lower than that of the surrounding impregnation, cavitation phenomena in impregnated paper insulation are considered a factor in degrading insulation performance. Consequently, this study analyzes the electrical conductivity of thermally aged materials and investigates the transient electric field characteristics within the cable. Additionally, it closely analyzes the formation and dissolution of cavities in MI cables during polarity reversal based on a numerical model of pressure behavior in porous media. The conductivity of the impregnated paper indicates that it has excellent resistance to thermal degradation. Simulation results for various load conditions highlight that the interval of load-off time and the magnitude of internal pressure significantly influence the cavitation phenomenon. Lastly, the study proposes stable system operation methods to prevent cavitation in MI cables. [ABSTRACT FROM AUTHOR]

Over the last few years, the petroleum giant and its partner have effectively implemented new marine seismic technologies in this part of the world. During the acquisition phase, the industry has observed the introduction of novel broadband acquisition techniques such as dual-sensor cable, multiple towed streamers (over/under), slanted and variable depth streamers, and isometric areal recording. The application of these techniques has resulted in a noteworthy enhancement of the recorded data's bandwidth. The focus of this paper is on the improvement of seismic bandwidth expansion resulting from advancements in marine broadband acquisition, innovative processing techniques, and inversion methodology. The outcome leads to a noteworthy enhancement in the vertical resolution, which proves to be valuable in the identification of thin stacked pay beds and the creation of a reservoir model that is constrained by seismic data. This paper focuses on the imaging aspect, particularly the complex structures. The utilization of wide and full azimuth (Circular) recording and the resolution of Gas wipeout issues through seabed acquisition with Ocean Bottom Cables (OBC) have been advantageous. By utilizing de-ghosted or far-field signature modeled techniques on the processing side, it is possible to increase the bandwidth for both legacy and modern high-quality data, such as Q-marine. A novel de-convolution technique has been developed, which can enhance signal frequency to a considerable extent while minimizing or eliminating any impact on noise. The article presents various wavelet transform techniques that can effectively enhance the signal-to-noise ratio (S/N). The methods are noteworthy due to their ability to be swiftly executed post-stack while incurring minimal expenses. Further, the inversion techniques, with a focus on stochastic elastic inversion, generates broadband data, enabling the identification of pay sand that falls below the quarter of wavelength criteria. The developed techniques are novel and have been validated using authentic Offshore Malaysia data. [ABSTRACT FROM AUTHOR]

The time–frequency-domain reflection method (TFDR) based on the Wigner–Ville distribution (WVD) is confronted with the problem of cross-term interference in existing methods to locate power cable defects. Therefore, a new method of locating cable defects based on Gaussian narrow-band envelope signals and the S-transform is proposed in this paper. In this method, the wide-band cable transfer function is obtained by adjusting the parameters of the Gaussian narrow-band envelope signal because the Gaussian narrow-band envelope signal has a good frequency-adjusting ability and time–frequency characteristics. Then, the time–frequency of the cable signal is transformed by the generalized S-transform, and the time delay of the modular matrix of the transformation matrix is estimated by the generalized cross-correlation algorithm to complete the accurate detection of the cable defect's location. Compared with traditional methods, the proposed method can adaptively adjust the analysis time width according to the frequency change and provide intuitive time–frequency characteristics without cross-term interference. Finally, the effectiveness and practicability of the proposed method are verified in MATLAB 2017_a by simulating a 40 m/10 kV medium-voltage power cable and submarine cable with a length of 32 km. [ABSTRACT FROM AUTHOR]

Similar to conventional ocean bottom seismometers and ocean bottom cables, the attitude and position of vertical cables deployed on the seafloor should be calibrated. However, due to the effect of ocean currents, the cable attitude is not stationary. Therefore, a new method for the dynamic repositioning of vertical cables is required. The dynamic repositioning of the hydrophones on vertical cables plays an important role in accurately describing the structure of the stratum and establishing an accurate velocity model. To realize the dynamic positioning of marine vertical cables, the shot lines are divided according to time, the first break time objective equation is established and the receiver position in each time period is obtained using the inversion methods outlined in this work. By analysing the trace spacing, first break time, shot point coordinate accuracy, temporal resolution, shot line spacing and other factors after repositioning, it is found that the first break time pickup accuracy and shot line spacing are the main factors that affect the repositioning accuracy. Furthermore, the resolution is limited by the timing of a single shot line. Additionally, the trace spacing after repositioning is consistent with the actual situation, which verifies the correctness and feasibility of this method. [ABSTRACT FROM AUTHOR]

Enhanced sedimentation at glacial margins can produce submarine megaslides (>10,000 km3). We report a single megaslide in the Surveyor Fan, Gulf of Alaska. Minimum extant size is ∼16,124 km2 in area and ∼9,080 km3 in volume. Slope failure occurred ∼1.2 Ma at the onset of the mid‐Pleistocene transition (MPT). With accretion along the Aleutian‐Alaska Trench, the original volume is conservatively ∼16,280 km3, with only a 140 km run‐out due to its blocky, high shear strength nature. We suggest the megaslide was triggered by a major sediment influx at the onset of the MPT, when glacial‐interglacial cycles shifted from 41 to 100 Kyr. The absence of repeat megaslides may reflect a changing balance between seismic strengthening and sediment flux, where later sedimentation driven by cross‐shelf ice streams results in thin, fluidized, non‐cohesive slides. Continued accretion of the Surveyor Fan and megaslide also reduces critical wedge taper, further inhibiting major failure. Plain Language Summary: Sediment flux at glacial margins can produce submarine slides >10,000 km3 in size (megaslides). We report a single megaslide in the Surveyor Fan, Gulf of Alaska. Minimum extant size is ∼16,124 km2 in area and ∼9,080 km3 in volume. Failure occurred ∼1.2 Ma at the onset of the mid‐Pleistocene transition (MPT). Due to accretion along the Aleutian‐Alaska Trench, the original volume is conservatively ∼16,280 km3, but with only a 140 km run‐out due to its blocky, high shear strength nature. We suggest the megaslide was caused by the initial major sediment flux at the onset of the MPT, and that afterward only fluidized, thin, and non‐cohesive slides occurred. This is due to changing balance between seismic strengthening and sediment flux, and accretion of the Surveyor Fan and megaslide which reduces the critical wedge taper inhibiting major failure. Key Points: World's Fifth largest mapped megaslide documented beneath Surveyor Fan Gulf of AlaskaTiming of slope failure linked to onset of mid‐Pleistocene glacial intensificationAbsence of later failures due to changing balance of sediment flux/seismic strengthening and negative feedbacks from critical wedge processes [ABSTRACT FROM AUTHOR]

Developing advanced underwater welding technology for titanium, which is the key structural material for underwater applications, is of great significance for the design, fabrication, and maintenance of submarine equipment. In this study, in order to investigate the underwater welding microstructure and mechanical properties of Ti-4Al-2V alloy, underwater wet laser welding was conducted on Ti-4Al-2V alloy using varying laser power. The microstructure and properties of the welding joints were characterized and analyzed. The microstructure of the heat-affected zone and fusion zone in the welding joints are not significantly different from those of welding in air, but a mixed oxide layer composed of Al2O3 and TiO2 is formed on the surface of the fusion zone. Due to internal stress, a large number of cracks initiate on the oxide layer and propagate to the joints. In the 4 kW and 5 kW joints, a penetrating crack formed due to the excessive accumulation of internal stress breaking up the α phase. The mechanical properties of the joints are significantly affected by the laser power. The tensile strength of the 3 kW and 4 kW joints is comparable to that of the base metal, which is about 600 MPa, while the 5 kW joint shows brittle fracture with no plastic deformation and 228 MPa strength. This research lays a solid foundation for understanding the underwater wet laser welding behavior of titanium alloys. [ABSTRACT FROM AUTHOR]

Under the current scouring, submarine cables are prone to be exposed, suspended, and even vortex‐induced vibration (VIV), threatening their mechanical and electrical properties. In this contribution, a finite element simulation model of 110‐kV single‐core optical fibre composite submarine cable is established. The natural frequency and resonant frequency of the model are obtained through wet mode analysis and harmonic response analysis. Then the VIV is simulated by the fluid–structure coupling method. Moreover, the stress extraction method of the torsional optical fibre position under the VIV is proposed. The results show that when the reduced speed is 2.57, the submarine cable appears beating vibration, which is composed of two vibrations with similar frequencies. When the reduced speed is 7.08, the vibration frequency is about 7.813 Hz, causing a rapid increase in vibration amplitude. The stress distribution of the torsional optical fibre presents a mirror image relationship at two moments separated by half a vibration cycle. Also, the frequency of stress change is the same as the frequency of VIV, which can judge whether the VIV occurs. The VIV range and position can be determined by the location where the stress changes the most. [ABSTRACT FROM AUTHOR]

Laying power cables along the bridge is a new way of laying submarine cables across the sea. Monitoring the health status of cables and their telescopic compensation devices is necessary. In this study, fiber grating sensing technology was used to monitor the strain, temperature, and vibration of the bridge cable of the Zhoushan–Daishan Bridge in Zhoushan, Zhejiang Province, and its compensation device. Two typhoons and one invasion event happened during the monitoring period. Temperature signals, strain signals, and time domain and time–frequency domain vibration signals were analyzed. The results showed that no fire hazards or risk of external damage were found with the bridge cable, and the monitoring system filled a gap in the in situ monitoring of the bridge cable in the Zhoushan–Daishan Bridge by the State Grid. [ABSTRACT FROM AUTHOR]

This study investigated the possible contributing factors to the digital gender divide and the spatial spillover effects of submarine communication cables on neighboring areas. Using spatial statistical models and global data, this study examined the Internet penetration rate and the digital gender divide in 186 countries. Data sources included open source data, social media, ITU and UNCTAD databases, and the World Bank. The study estimated the average male and female Internet users in 186 countries using Facebook API. The number of submarine communication cables between countries was used as the basis for constructing the spatial weights matrix. The countries with the highest Internet penetration rate were mostly in Europe. Those with the lowest Internet penetration rate were in Africa, Central Asia, and West Asia. Thirteen of the 15 countries with the worst Internet penetration rate were located in the African region. A significant digital gender divide arose in the developing and the least-developed countries. We argue that connectivity is key to the reduction of the digital gender divide and to ensuring that more women have access to the Internet. The study ascertains that the Internet penetration rate is related to the digital gender divide in individual countries and has a spatial spillover impact in surrounding nations connected by submarine communication cables. The study demonstrates that submarine cables serve as important infrastructure for closing the digital gender divide and deserve increased analytical attention. [ABSTRACT FROM AUTHOR]

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